Focal-plane camera shutter mechanism



Oct. 25, 1938. A. c. MAYO ET AL FOCAL-PLANE CAMERA SHUTTER MECHANISM Filed Jan. 11, 1938 2 Sheets-Sheet l l INVENTORS flu zsn Cebu-k Mara .w

Jassm TERRETT Oct. 25, 1938. A. c. MAYO ET AL 2,134,309

FOCAL-PLANE CAMERA SHUTTER MECHANISM Filed Jan. 11, 1958 2 Sheets-Sheet 2 l N V EN TO 25 IU-Pza Ckacz Mm: and

floss/w TERRETT M,M 1M

Patented Cd. 25, 1938 i I 2,134,309

UNITED STATES PATENT OFFICE FOCAL-PLANE CAMERA SHUTTER MECHANISM Alfred Croger Mayo, Richmond, and Joseph Terrett, London, England, assignors to Purina. Cameras Limited, London, England, a British company Application January. 11, 1938, Serial No. 184,424

In Great Britain February 6, 1937 4 Claims. (Cl. 95-55) This invention comprises improvements in or Figure l is a longitudinal central section relating to focal-plane camera shutter mechathrough a camera; nism. In United States Patent No. 2,017,979 Figure 2 is an elevation of a camera from the there is described a camera having a curved back with the back cover and guide-plate re- 5 back-plate behind which the film passes and a moved, and 6 sliding shutter-plate working close to the film Figures 3, '4 and 5 are details showing the surface on the other side of the back-plate and shutter-plate in various positions. which is released for movement across an ex- The generalarrangement of the parts of the posure-aperture in the back-plate by means of camera is similar to that described in the afore- 10 a trigger. A second plate in contact with the said United States patent, but the construction 10 shutter-plate can be operated to modify the illustrated is arranged to be a p from width of a slit in the shutter plate so as to vary mouldable material instead of being built up from the efiective amount of the exposure. sheet steel. The camera has two flat side plates The present invention relates to a shutter I I, i2 between which extends a front l3, moulded having a sliding shutter-plate and a variable n o 'pi w h t si p s nd rr n a 15 width of slit and has for its object the simplilsns'mount l4. The lens mount is c pa e of fication of the means for modifying the width of being slid le p y n h nt 3 an i the slit. yieldingly pressed forward by a spring 15. It is According to the present invention upon the held inward by a cap when the camera is not in sliding shutter-plate there is mounted a second se; s described in the aforesaid Patent All 20 plate for modifying the width of the slit and a the back of the lens mount there is a diaphragm weight-actuated mechanism operatively interplate I 6 pierced wi h a rec n l r p r re f r connecting the shutter-plate and the sliding the passage of the light from the lens. plate thereon to determine their relative p0si- Behind the front plate 13 and extending from tions and thereby the width of the slit. In this s to s w n side pl there i a 26 way when the camera is held in one position the C ve film de-p t having a p u weight will cause the mechanismto afford one aperture 0f the desired Size of the pictures to width of slit and when the camera is held in a be taken y the fl- The -P ate IT is difierent position in relation to the horizontal oncave 0n the side towards the lens so that in the weight will cause another width of slit to be t centre p where t t -ap tur s. 30 afforded it is close to the back IQ of the camera, while Conveniently the mechanism operatively contowards its ends it sweeps forward close behind necting the shutter-plate and the sliding adjuste front p at l3 s s t Come in front of and ment plate thereon is constituted by a cam and s e d Ofl t e mountings 20, 2| which are W0- preferably the cam is pivoted and made of such Vldsd for e fi D O The gu de-p ate 1 35 form as to be highly eccentric to its pivot and rests on inwardly projecting locating s or heavy enough to itself constitutethe operating fl n s 23 u e which serve to locate it weight accurately in position and it is secured by lugs The present invention is herein described as 25 Testing 011 hmuldsd ut ts 6, 2 It incorporated in a camera such as that described Will be. Observed that the guidedilate is t 40 in co-pending United States patent application ened a little on each side of the picture-aperture Serial No. 150,924, filed on June 29, 1937, in the s indicated at so t t fi wh ch name of one of the present applicants and it is D S Over the d -p s flattened Where to be understood that no claim is made herein it Comes pp the picture-aperture. although to the invention described in the said co-pending t guide-plate even Over the thickened P t s 45 application, the present invention being limited 8, 29 is still slightly concave towards t s, to the weight-actuated shutter adjustment as set o h not enough to Carry the film sensibly forth in the appended claims. The invention is ut f the plane of focus of the lens- A p i not, however, limited to its employment in a 30 on the back I9 of the camera serves to press camera of the type described and the following the film closely against the guides. Number- 50 is a description, by way of example only, of one windows 3|, 32 are provided in the camera back. construction in accordance with the invention as A film-winder 33 is provided but is let flush into incorporated in the camera described in the the side wall I! of the camera. This side wall aforesaid application. is moulded considerably thicker than the other In the accompanying drawings:-- side wall ll so as to permit the operating parts 55 1 in the norm "7 with a hook it in Figure 2.

to be located flush within the thickness of the side wall. An optical view-finder 34 is also located within the thickness of this wall.

The back cover-plate I9 is, of course, made readily detachable for loading purposes and is made to fit in a. light-tight manner against the side walls and front l3 of the camera.

In front of the guide-plate II the side walls H, have further inwardly projecting ledges 35, 36 which are spaced somewhat fronrthe guide plates l1 and in this space the edges of a curved shutter-plate 31 are guided so as to slide freely. The shutter-plate 31 is provided with an abutment 38 which can be engaged,

" when the shutter-plate is at one extremity of its movement by a strip. member 39 formed as part of a flat spring 49 secured to the side plate H of the camera. The trip member is operatively connected to a release-trigger 4| the heed of which projects through the side-plate l2 to the outside thereof. The connections between the release-"7' the trip 39 comprise a head of the trigger 4|, which head rtion of the spring 40, but ion of the trigger is se arated therefrom by a ertain space so that is a lost-motion before the trigger operates the trip. The shutter-plate 3'1 is urged in a direction away from that in which it would be held by the tripmember 39, that is to say in a downward direction in Figures 1 and 2, by means of a shutter spring 44 and it capable of being wound back against the spring 64 into the set" position by a lever pivoted at 46, 41 in the side-plates ii, i2 and connected to a setting arm 45 recessed into the outside of the side-plate 12. The setting lever 45 is operatlvely connected to the shutter-plate 3'! by a link 49 pivoted to the shutter-plate at 50 (Figure 3) and provided El slot |52 in the lever 45. This makes a ti. achaole slot connection with the lever 45, which is very convenient in assembling the parts. It will be observed that the pivots 46, of the setting lever 45 lie on an ..T axis which is parallel to the axis of curvature of the shutter-plate 3? and that the shutter spring M acts on the shutter through the intermediary of the lever 45 and the link 49.

The shutter piate itself is provided with an exposure-slit 52, best seen lnFlgure 5, although also visible in Figure 1. If this were the whole of the shutter mechanism it would, of course, be impossible to set the shutter-plate 3! by means of the setting lever mechanism 48, 45 without first capping the lens; otherwise the film would l of the diaphragm plate l6 at the back of the lens mount and is capable, as shown in Figure 2, of closing the aperture in the diaphragm, or alternatively of being swung out of the way by movement in the direction of the arrow marked upon The edge of the safety shutter 56 which is remote from the pivot 55 enters beneath an overlapping lug 56 on the diaphragm plate i6 when the plate is closed and this keeps it closed against the diaphragm plate. The stem t3 of the trigger 4| carries a laterally projecting lug which is pivoted at 51 between an arm 38 and a second arm 59 projecting from the safety shutter -1. The length of this arm, relatively to the extent of movement permitted to the trigi'fi er 4: is such as to give a velocity ratio between the movement of the trigger and the movement of the safety shutter adequate to move the safety shutter completely out of the way 01 the lens |4 before the lost-motion between the foot 42 of the stem 43 and the spring 40 has been taken up and the shutter-plate 3! released. The return of the trigger 4| and of the safety shutter 54 to the position shown in Figure 2, when pressure on the trigger is released, is ensured by a spring 60 engaged at one end with the stem 43 of the trigger and at the other end with the extremity of the arm 56. On the front of the shutter-plate 3'! is mounted a smaller sliding plate 6| for varying the width of the exposureslit 52 in the shutter-plate. This auxiliary sliding plate 6| has an aperture 62, one edge 63 of which is capable of being moved so as to overlap more or less the exposure-slit 52. It is held on the shutter-plate by overlapping lugs 64. Three different widths of slit are shown in Figures 3, 4 and 5 corresponding to different positlons of adjustment of the sliding plate 6|.

In the drawings there is illustrated means for moving the sliding shutter-plate which comprise a heart-shaped cam 65 pivoted at 66 in the shutter-plate 31. The cam 65 is made sufllciently heavy always to hang with its rounded point lowermost. This presses against an upturned edge 61 of the sliding plate 6|. When the camera is held upright in the positions shown in Figures 1, 2 and 3 the point of the cam presses the sliding plate 6| to the position where the exposure-slit is narrowest. If the camera is turned in a horizontal position, either side up. the cam will assume a position such as is illus trated in Figure 4, in which the sliding plate is permitted to move to a position where the slit is wider, and if the camera is inverted the parts assume the position shown in Figure 5, where the exposure-slit is at its widest. No spring is provided for drawing the sliding plate 6| against the cam because the inertia of the plate causes it to lag behind the movements 01' the shutterplate 31 even when the camera is held horizontally, and during the exposure movement of the shutter when the trigger 4| is pressed this carries the upturned edge 61 back into firm engagement with the cam. When the camera is held vertically the weight of the sliding plate 6| ensures it occupying the position shown.

It will be observed that there is a recess in the safety shutter-plate 54 which is co-axlal with the lens mount 4. The purpose of this recess is to receive the back of the lens mount when the latter is pressed back into the camera by the use of the cap over the shutter and to thereby cause the lens mount to interlock with the shutter member and prevent operation of the shutter when the cap is in place.

There may be provided in accordance with the present invention means to intercept temporarily the motion of the curved shutter-plate 31 at the point at which the exposure-aperture 32 therein coincides with the picture-aperture H3 in the guide-plate H. In this event the aperture 52 must be made as wide as the picture-aperture l8 and if the movement is thus intercepted a time exposure is made, the exposure being terminated by release of the trigger 4| which allows the auxiliary shutter-plate to return to the position in which it closes the light-aperture in the diaphragm of the front plate l3.

It will be found that the location of the trigger 4| for the release of the shutter is convenient when the user of the camera is holding it close to his eye so that he can look through the view-finder 34 because the trigger 4| comes into a convenient position for operation by the forefinger of the hand holding the camera.

We claim:-

1. In a camera the combination with a slidable shutter-p1ate, an exposurc-slit therein and means for moving the shutter-plate to make on exposure of means for modifying the width of the slit comprising a second plate mounted upon the shutterplate so as to he movable relatively thereto and to overlap the slit more or less in combination with a pendulous weight mounted upon one of the said plates and mechanism operatively interconnecting the pendulous weight and the other said plate to determine the position of the sliding plate relatively to the slit.

2. In a camera the combination of a guideplate having a picture aperture therein and mounted close to the focal plane, a shutter-plate mounted to slide over the guide-plate and having an exposure-slit therein, means for moving the shutter-plate over the guide-plate to make an exposure, an exposure-modifying plate mounted upon the shutter-plate and movable relatively thereto so as to be capable of overlapping the slit more or less and a pendulous weight upon the shutter-plate which weight is operatively connected to the exposure-modifying plate thereon to determine the width of the slit.

3. In a camera the combination of a guideplate having a picture-aperture therein, said guide-plate being located close to the focal plane of the camera, a shutter-plate mounted to slide over the guide-plate and having an exposureslit therein, means for moving the shutter-plate over the guide-plate to make an exposure, an exposure-modifying plate slidably mounted on the shutter-plate so as to be capable of overlapping more or less the width of the slit, and a cam pivotally disposed upon the shutter-plate so as to bear against the exposure-modifying plate, said cam being so weighted as to rotate relatively to the shutter-plate to different positions according to the position of the camera relative to the horizontal and thereby to modify the width of the exposure-slit.

4C. In a camera as claimed in claim 3, the arrangement wherein the weighted cam lies behind the part of the exposure-modifying plate against which it abuts, considered in the direction of movement of the shutter in making an exposure so that the eiTect of inertia upon commencement of the shutter movement tends to press the exposure-modifying plate toward the cam.

ALFRED CROGER MAYO. JOSEPH TERRET'I'. 

